According to electoral-vote.com, giving Clinton 3% more ties her in New Mexico and wins her in Kentucky.

Giving Obama 3% more wins him PA and NC, brings him within 1% in Ohio, and ties him in NH.  Oh, and wins him TX.

Many of the polls relied on there are out of date by now, so your mileage may vary.  I'd take this not as a sign that one candidate is better than another, but as a sign that McCain's really in trouble once the nomination's settled.